Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Que tipo de estrutura há na Torre de Natal Americana?
 ###Tabelas: CREATE TABLE structures_past_or_present_between_500_and_550_m_1640_and_1804_ft (structures_past_or_present_between_500_and_550_m_1640_and_1804_ft_id AUTO_INCREMENT PRIMARY KEY, Name VARCHAR, Pinnacle height VARCHAR, Structure type VARCHAR, Main use VARCHAR, Country VARCHAR, Town VARCHAR) CREATE TABLE 2010_team (2010_team_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, Position VARCHAR, School VARCHAR, Hometown VARCHAR, College VARCHAR) CREATE TABLE football_league_first_division (football_league_first_division_id AUTO_INCREMENT PRIMARY KEY, Date VARCHAR, Opponent VARCHAR, Venue VARCHAR, Result VARCHAR, Attendance INT) CREATE TABLE buildings_above_140m (buildings_above_140m_id AUTO_INCREMENT PRIMARY KEY, Rank VARCHAR, Name VARCHAR, City VARCHAR, Height in m (ft) VARCHAR, Floors INT, Year built INT) CREATE TABLE boys'_basketball_players_and_coaches_of_the_year (boys'_basketball_players_and_coaches_of_the_year_id AUTO_INCREMENT PRIMARY KEY, Year VARCHAR, Player VARCHAR, School VARCHAR, Hometown VARCHAR, College VARCHAR, NBA Draft VARCHAR)  
SELECT Structure type FROM structures_past_or_present_between_500_and_550_m_1640_and_1804_ft WHERE Name = american tower christmas